Modern physics deals with some ridiculously non-intuitive stuff. Objects act as though they gain mass the faster they move. An electron can’t decide if it’s a particle, a wave or both. However, there is one statement that takes the cake on sounding like crazy talk: Empty space isn’t empty.

If you take a container, pump all the air out of it, shield it from electric fields and plop it in the deepest of intergalactic space to get it away from gravitational fields, that container should contain absolutely nothing. However, that’s not what happens.

At the quantum scale, space is a writhing, frantic, ever-changing foam, with particles popping into existence and disappearing in the wink of an eye. This is not just a theoretical idea—it’s confirmed. How can this bizarre idea be true?

Even though in classical physics we are taught that energy is conserved, which means it cannot change, one of the tenets of quantum mechanics says that energy doesn’t have to be conserved if the change happens for a short enough time. So even if space had zero energy, it would be perfectly OK for a little energy to pop into existence for a tiny split second and then disappear—and that’s what happens in empty space. And since energy and matter are the same (thank Einstein for teaching us that E=mc2 thing), matter can also appear and disappear.

And this appears everywhere. At the quantum level, matter and antimatter particles are constantly popping into existence and popping back out, with an electron-positron pair here and a top quark-antiquark pair there. This behavior is the reason that scientists call these ephemeral particles “quantum foam”: It’s similar to how bubbles in foam form and then pop.